It is the high-tech equivalent of putting your thumb in the biggest piece of pizza when your brother opens the box, to claim it as your own.
2) Before shredders got good. You put the luminol dust on the steering wheel of an inteligence officer's car. Then you steel the shredded paper from the base. The luminol then identifies which shreds of paper come from documents handled by the inteligence officer.
3) You dope the inteligence officer's car again. Then you look at the door punchcode panel to see which buttons he pressed. Now you are 90% of the way to knowing the code.
It gives the farmer quite a lot of information, by changing the color every 17 days (a ewe's cycle), they can detect a infertile tup, predict lambing dates, etc.
I would expect shredders these days to be easily defeated with a scanner and some clever algorithms. Is that not the case?
Isn't Bluestar better than Luminol?
> KGB defector Yurchenko, who defected to the U.S. that same year, had confirmed that the KGB not only continued to employ spy dust, but was also experimenting with other powerful tracking substances and techniques under a top-secret umbrella program called METKA. We understood that spy dust could be used to track the Soviets' own citizens as well; it could be very useful in picking an individual out of a crowd, even at night, or in bad weather. A special light was used to illuminate and spot the tiny chemical particles, which, when used in small amounts, could be nearly invisible to the naked eye. Typically the technical readout would be performed at a chokepoint that the KGB controlled. The entrance to the U.S. Embassy compound, manned by the Soviet Militia, or a bridge over a well-traveled corridor were the sort of locations where a light and optics unit could be mounted.
The wikipedia article also mentions luminol (a different chemical), so it is hard to be sure whether references to UV refer to luminol instead. I'm not sure if both chemicals glow under UV.
Nevertheless, wikipedia also links to a NY Times article from 1986 (https://www.nytimes.com/1986/02/15/world/us-says-spy-dust-us...) which says, "The ''spy dust'' reportedly glowed under ultraviolet light." So unless the NY Times got them mixed up, it sounds like "regular" (non-luminol) spy dust glows too.
Of course, the wikipedia article also mentions a method that involves collecting a chemical sample, so it's possible they might have also used it to detect residue to check whether a spy touched some object.
I guess these days they just put a dash of Polonium-210 in your tea and follow you with a Gieger counter, sends a much stronger message.
MEMS camera "dust" with a/v recording, storage, and GNSS would be nice.